init commit: 0.1.0

.envrc

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+use flake

.gitignore

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+.direnv/*
+/target
+result

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "heck"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "95505c38b4572b2d910cecb0281560f54b440a19336cbbcb27bf6ce6adc6f5a8"
+
+[[package]]
+name = "nixos-reedsreboot"
+version = "0.1.0"
+dependencies = [
+ "strum",
+ "strum_macros",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.78"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2422ad645d89c99f8f3e6b88a9fdeca7fabeac836b1002371c4367c8f984aae"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.35"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "291ec9ab5efd934aaf503a6466c5d5251535d108ee747472c3977cc5acc868ef"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "rustversion"
+version = "1.0.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7ffc183a10b4478d04cbbbfc96d0873219d962dd5accaff2ffbd4ceb7df837f4"
+
+[[package]]
+name = "strum"
+version = "0.26.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "723b93e8addf9aa965ebe2d11da6d7540fa2283fcea14b3371ff055f7ba13f5f"
+
+[[package]]
+name = "strum_macros"
+version = "0.26.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7a3417fc93d76740d974a01654a09777cb500428cc874ca9f45edfe0c4d4cd18"
+dependencies = [
+ "heck",
+ "proc-macro2",
+ "quote",
+ "rustversion",
+ "syn",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.52"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b699d15b36d1f02c3e7c69f8ffef53de37aefae075d8488d4ba1a7788d574a07"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3354b9ac3fae1ff6755cb6db53683adb661634f67557942dea4facebec0fee4b"

Cargo.toml

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+[package]
+name = "nixos-reedsreboot"
+version = "0.1.0"
+edition = "2021"
+description = "Determine if you need to reboot your NixOS machine"
+license = "GPL-2.0"
+repository = "https://github.com/thefossguy/nixos-reedsreboot"
+readme = "README.md"
+keywords = [ "nixos" ]
+categories = [ "command-line-utilities" ]
+
+[dependencies]
+strum = "0.26"
+strum_macros = "0.26"

README.md

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+# nixos-needsreboot
+
+Checks if you should reboot your NixOS machine in case an upgrade brought in
+some new goodies. :)

flake.lock

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+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1709309926,
+        "narHash": "sha256-VZFBtXGVD9LWTecGi6eXrE0hJ/mVB3zGUlHImUs2Qak=",
+        "rev": "79baff8812a0d68e24a836df0a364c678089e2c7",
+        "revCount": 556338,
+        "type": "tarball",
+        "url": "https://api.flakehub.com/f/pinned/NixOS/nixpkgs/0.2311.556338%2Brev-79baff8812a0d68e24a836df0a364c678089e2c7/018dfea4-6d6e-74d3-b5df-3d859de1988e/source.tar.gz"
+      },
+      "original": {
+        "type": "tarball",
+        "url": "https://flakehub.com/f/NixOS/nixpkgs/%2A.tar.gz"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

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+{
+  inputs = {
+    # a better way of using the latest stable version of nixpkgs
+    # without specifying specific release
+    nixpkgs.url = "https://flakehub.com/f/NixOS/nixpkgs/*.tar.gz";
+  };
+
+  outputs = { self, nixpkgs, ... }:
+    let
+      # helpers for producing system-specific outputs
+      supportedSystems = [
+        "aarch64-linux"
+        "riscv64-linux"
+        "x86_64-linux"
+      ];
+      forEachSupportedSystem = f: nixpkgs.lib.genAttrs supportedSystems (system: f {
+        pkgs = import nixpkgs { inherit system; };
+      });
+    in
+    {
+      devShells = forEachSupportedSystem ({ pkgs, ... }: {
+        default = pkgs.mkShell {
+          packages = with pkgs; [
+            rustup
+            gdb
+            pkg-config
+
+            # formatting this flake
+            nixpkgs-fmt
+          ];
+        };
+      });
+
+      packages = forEachSupportedSystem ({ pkgs, ... }: {
+        default = pkgs.rustPlatform.buildRustPackage {
+          pname = "nixos-needsreboot";
+          version = "0.1.0";
+          src = ./.;
+
+          cargoHash = "sha256-5b8db/Jy17u+olpJy4aeR7BO7m01yxzg++ar2u5gYk0=";
+        };
+      });
+    };
+}

src/compare_nixos_modules.rs

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+use std::{error::Error, fmt, fs};
+use strum::IntoEnumIterator;
+use strum_macros::EnumIter;
+
+use crate::{NEW_SYSTEM_PATH, OLD_SYSTEM_PATH};
+
+#[derive(EnumIter)]
+enum ModuleType {
+    LinuxKernel,
+    Systemd,
+}
+
+// for printing messages
+impl fmt::Display for ModuleType {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Self::LinuxKernel => write!(f, "Linux Kernel"),
+            Self::Systemd => write!(f, "Systemd"),
+        }
+    }
+}
+
+// for getting the "suffix"
+impl fmt::Debug for ModuleType {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Self::LinuxKernel => write!(f, "/kernel"),
+            Self::Systemd => write!(f, "/system"),
+        }
+    }
+}
+
+impl ModuleType {
+    fn get_nix_store_path(&self, use_old_path: bool) -> Result<String, Box<dyn Error>> {
+        let suffix = match self {
+            Self::LinuxKernel => "/kernel",
+            Self::Systemd => "/systemd",
+        };
+        let strip_suffix = match self {
+            Self::Systemd => false,
+            Self::LinuxKernel => true,
+        };
+
+        let system_path = if use_old_path {
+            OLD_SYSTEM_PATH.to_string()
+        } else {
+            NEW_SYSTEM_PATH.to_string()
+        };
+
+        let tmp_module_path = fs::read_link(system_path + suffix)?
+            .into_os_string()
+            .into_string()
+            .expect("Cannot convert PathBuf to String");
+
+        let nix_module_path = if strip_suffix {
+            let split_module_path = tmp_module_path.split('/').collect::<Vec<&str>>();
+            let mut module_dir = split_module_path
+                .get(1..4)
+                .ok_or("Cannot find the module's directory in /nix/store")?
+                .join("/");
+            module_dir.insert(0, '/');
+            module_dir
+        } else {
+            tmp_module_path
+        };
+
+        Ok(nix_module_path)
+    }
+
+    fn get_linux_version(linux_path: &str) -> Result<String, Box<dyn Error>> {
+        let lib_modules_path = fs::read_dir(linux_path)?
+            .nth(0)
+            .ok_or("Expected one directory in ".to_string() + linux_path)??
+            .path()
+            .into_os_string()
+            .into_string()
+            .expect("Cannot convert PathBuf to String");
+        let linux_version = lib_modules_path.split('/').nth(6).ok_or(
+            "Could not determine Linux kernel version from path: ".to_string() + &lib_modules_path,
+        )?;
+
+        Ok(linux_version.to_string())
+    }
+
+    fn get_systemd_version(systemd_path: &str) -> Result<String, Box<dyn Error>> {
+        let split_systemd_path = systemd_path.split('-').collect::<Vec<&str>>();
+        let systemd_version = split_systemd_path
+            .get(2..)
+            .ok_or("Could not determine Systemd version from path: ".to_string() + systemd_path)?
+            .join("-");
+        Ok(systemd_version)
+    }
+
+    fn get_version(&self) -> Result<(String, String), Box<dyn Error>> {
+        let old_module_root_path = self.get_nix_store_path(true)?;
+        let new_module_root_path = self.get_nix_store_path(false)?;
+
+        let old_module_version: String;
+        let new_module_version: String;
+
+        match self {
+            Self::LinuxKernel => {
+                let linux_path = old_module_root_path + "/lib/modules";
+                old_module_version = Self::get_linux_version(&linux_path)?;
+                new_module_version = Self::get_linux_version(&linux_path)?;
+            }
+            Self::Systemd => {
+                old_module_version = Self::get_systemd_version(&old_module_root_path)?;
+                new_module_version = Self::get_systemd_version(&new_module_root_path)?;
+            }
+        }
+
+        Ok((old_module_version, new_module_version))
+    }
+}
+
+pub fn upgrades_available() -> Result<bool, Box<dyn Error>> {
+    let mut needs_reboot = false;
+    'x: for module in ModuleType::iter() {
+        let (mut old_module_version, mut new_module_version) = module.get_version()?;
+
+        if old_module_version != new_module_version {
+            if old_module_version.len() != new_module_version.len() {
+                if old_module_version.contains("-rc") && !new_module_version.contains("-rc") {
+                    old_module_version = old_module_version.replace("-rc", ".");
+                    new_module_version.push_str(".0");
+                } else if new_module_version.contains("-rc") && !old_module_version.contains("-rc")
+                {
+                    new_module_version = new_module_version.replace("-rc", ".");
+                    old_module_version.push_str(".0");
+                } else if new_module_version.contains("-rc") && old_module_version.contains("-rc") {
+                    new_module_version = new_module_version.replace("-rc", ".");
+                    old_module_version = old_module_version.replace("-rc", ".");
+                }
+            }
+
+            let old_version = &old_module_version.split('.').collect::<Vec<&str>>();
+            let new_version = &new_module_version.split('.').collect::<Vec<&str>>();
+
+            for (old, new) in old_version.iter().zip(new_version.iter()) {
+                if new > old {
+                    eprintln!("DEBUG: needs upgrading for module '{module}'");
+                    needs_reboot = true;
+                    break 'x;
+                }
+            }
+        }
+    }
+
+    Ok(needs_reboot)
+}

src/main.rs

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+use std::error::Error;
+use std::fs;
+
+mod compare_nixos_modules;
+
+pub static OLD_SYSTEM_PATH: &str = "/run/booted-system";
+pub static NEW_SYSTEM_PATH: &str = "/nix/var/nix/profiles/system";
+
+fn main() -> Result<(), Box<dyn Error>> {
+    if std::path::Path::new("/nix/var/nix/profiles/system").exists() {
+        let old_system_id = fs::read_to_string(OLD_SYSTEM_PATH.to_string() + "/nixos-version")?;
+        let new_system_id = fs::read_to_string(NEW_SYSTEM_PATH.to_string() + "/nixos-version")?;
+
+        if old_system_id == new_system_id {
+            eprintln!("DEBUG: you are using the latest NixOS generation, no need to reboot");
+        } else if compare_nixos_modules::upgrades_available()? {
+            fs::File::create("/var/run/reboot-required")?;
+        } else {
+            eprintln!("DEBUG: no updates available, moar uptime!!!");
+        }
+    } else {
+        eprintln!("This binary is intedned to run only on NixOS.");
+    }
+
+    Ok(())
+}